Understanding cognitive impairment in mood disorders: mediation analyses in the UK Biobank Cohort

Cullen, B. , Smith, D. J. , Deary, I. J., Pell, J. P. , Keyes, K. M. and Evans, J. J. (2019) Understanding cognitive impairment in mood disorders: mediation analyses in the UK Biobank Cohort. British Journal of Psychiatry, 215(5), pp. 683-690. (doi: 10.1192/bjp.2019.188) (PMID:31412972)

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Background: Cognitive impairment is strongly linked with persistent disability in people with mood disorders, but the factors that explain cognitive impairment in this population are unclear. Aims: To estimate the total effect of (a) bipolar disorder and (b) major depression on cognitive function, and the magnitude of the effect that is explained by potentially modifiable intermediate factors. Method: Cross-sectional study using baseline data from the UK Biobank cohort. Participants were categorised as having bipolar disorder (n = 2709), major depression (n = 50 975) or no mood disorder (n = 102 931 and n = 105 284). The outcomes were computerised tests of reasoning, reaction time and memory. The potential mediators were cardiometabolic disease and psychotropic medication. Analyses were informed by graphical methods and controlled for confounding using regression, propensity score-based methods and G-computation. Results: Group differences of small magnitude were found on a visuospatial memory test. Z-score differences for the bipolar disorder group were in the range −0.23 to −0.17 (95% CI −0.39 to −0.03) across different estimation methods, and for the major depression group they were approximately −0.07 (95% CI −0.10 to −0.03). One-quarter of the effect was mediated via psychotropic medication in the bipolar disorder group (−0.05; 95% CI −0.09 to −0.01). No evidence was found for mediation via cardiometabolic disease. Conclusions: In a large community-based sample in middle to early old age, bipolar disorder and depression were associated with lower visuospatial memory performance, in part potentially due to psychotropic medication use. Mood disorders and their treatments will have increasing importance for population cognitive health as the proportion of older adults continues to grow.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Smith, Professor Daniel and Evans, Professor Jonathan and Cullen, Dr Breda and Pell, Professor Jill
Authors: Cullen, B., Smith, D. J., Deary, I. J., Pell, J. P., Keyes, K. M., and Evans, J. J.
College/School:College of Medical Veterinary and Life Sciences > School of Health & Wellbeing > Mental Health and Wellbeing
Journal Name:British Journal of Psychiatry
Publisher:Royal College of Psychiatrists
ISSN (Online):1472-1465
Published Online:15 August 2019
Copyright Holders:Copyright © 2019 The Royal College of Psychiatrists
First Published:First published in British Journal of Psychiatry 215(5):683-690
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
666301Cognitive outcomes in people with behavioural and brain disorders within UK BiobankBreda CullenOffice of the Chief Scientist (CSO)DTF/14/03IHW - MENTAL HEALTH & WELLBEING
3029570Mental Health Data PathfinderDaniel SmithMedical Research Council (MRC)MC_PC_17217HW - Mental Health and Wellbeing